Worked Example: Search & Tutoring Systems

A Perplexity-style AI search engine needs to search the web, synthesize an answer with real citations, and do it for a million queries a day with genuine real-time freshness. This is RAG, but with two twists Tier 8 did not have to deal with directly: the corpus is the entire live web, not a fixed document set, and citations are not a nice-to-have, they are the entire product.

The synthesis prompt has to force citations structurally, "answer using only information from the provided sources, and cite [Source N] after every claim", the exact grounded-generation pattern from Tier 8's citation tracker chapter. And exactly as in that chapter, generating a citation is not the same as generating a correct one: an output guard has to verify every single [Source N] reference actually maps to a real retrieved source before the answer ever reaches the user.

Tier 10's caching chapter treated a 24-hour TTL as a reasonable default. A search engine promising real-time freshness cannot use that default. A cache TTL of an hour or less is the tradeoff this specific product actually needs, accepting a meaningfully lower cache hit rate, and therefore higher cost, in exchange for answers that do not go stale on fast-moving news. This is exactly the kind of requirement-specific tuning step 1 of the framework exists to surface before a design gets built around the wrong default.

500,000 students across 20 subjects, each learning at a genuinely different pace, is precisely the personalization problem Tier 9's long-term memory chapter was built for, applied here to tracking what a specific student does and does not yet understand, rather than what a specific user prefers for dinner.

This is the same paranoid-sensitivity guardrail configuration from Tier 7's safety chapter and Tier 10's production guardrails chapter, applied here without exception, since the users are children. Every response passes through age-appropriate content checking before it ever reaches a student, with no lower-stakes exception carved out anywhere in this particular system.